Traditional energy sources (e.g., oil, natural gas, and coal) are limited, non-renewable and depleting rapidly. Thus, utilization of renewable energy sources such as wind energy, fuel cell, solar energy, etc. has gained importance. Wind based energy conversion systems for providing wind-generated power to electrical power grids are currently experiencing tremendous growth and increased popularity. In particular, wind energy conversion systems convert the kinetic energy of wind into electricity or other forms of energy. Moreover, utilization of wind power is a fast growing power generation technology, which has been recognized as an environmentally friendly means of power generation.
The major components of a typical wind energy conversion system (WECS) include a wind turbine, generator, interconnection apparatus and control systems. Typically, traditional systems include synchronous generators, permanent magnet synchronous generators, and/or induction generators (e.g., squirrel cage type and wound rotor type generators for wind turbines). Further, the interconnection apparatus includes power electronic converters that can achieve power control, soft start and interconnection functions. Generally, both voltage source converters (VSC) and current source converters (CSC) can be used in a WECS.
Various traditional topologies are available for VSC and CSC based WECSs. Typically, VSC based topologies include an interconnection system comprising a diode rectifier, a boost converter and a Pulse Width Modulated (PWM) Voltage Source inverter (VSI), or an interconnection system comprising a diode rectifier with a PWM VSI, or an interconnection system comprising back to back PWM VSIs. Further, traditional CSC based topologies include an interconnection system that employs a diode rectifier and a phase-controlled thyristor inverter, or an interconnection system that employs back-to-back phase-controlled thyristor based converters, or an interconnection system that employs back-to-back PWM CSCs. However, most traditional topologies involve a number of expensive active semiconductor devices, utilized within a generator-side converter. In other traditional topologies, which employ a diode rectifier with a PWM VSI, a voltage-boost circuit is utilized that can add to the cost and complexity of the system and control.